Ovine pulmonary carcinoma (OPC) is a contagious lung tumor of sheep that originates from type II alveolar epithelial cells and strikingly resembles bronchioloalveolar carcinoma (BAC) of humans. Morphological, biochemical, and immunological data implicate a type D retrovirus as the cause of OPC, but this virus has not yet been propagated in cell culture. With the expectation that OPC will prove to be a valuable model of a retrovirus-induced pulmonary neoplasia that may lead to a greater understanding of pulmonary carcinogenesis we propose to: 1) Examine the distribution of the OPC virus within tumor cells to determine whether the viral generation is exogenous or endogenous, whether the virus is clonally integrated in the tumor cells, and to develop appropriate approaches for dissecting the mechanism of oncogenesis; and 2) Evaluate OPC viral product expression in infected animals prior to and after the onset of neoplastic sequelas. The experimental design is based on initially generating the appropriate reagents-molecular and immunological probes as well as tissues from animals from initial infection through the development of neoplastic sequelae. This will then be applied to correlate the viral life cycle (integration, expression and regulation) to the neoplastic processes. The methods to be used include: nucleic acid hybridizations, both from tissues (Southern and Northern blots, RNA dot blots) and in specific sites (in situ hybridization); and parallel immunological assays (ELISAs), immuno-histochemistry and Western blots). Reagents will be developed using the polymerase chain reaction for isolation, testing and cloning probes, and sequencing; generation of recombinant antigens will result from these clones and will be used along with purified viral components to generate OPC viral antisera. All of these techniques have been done by the investigators involved. Similar studies, in some cases without the advantage of the newer techniques, have been used with success in other studies of retroviral-associated neoplasia.